1. Field of the Invention
The present invention relates to a wideband indium antimonide (InSb) photodetector device having a passivated light receiving surface which eliminates the degradation of photoresponse in the infrared region due to flashing and enables the photodetector to detect visible as well as infrared light radiation.
2. Description of the Related Art
Back-side illuminated InSb photodetector devices such as photodiode arrays have been conventionally used for detecting infrared light radiation having wavelengths between 1 and 5.5 micrometers. However, they have been unusable for detecting light both in the visible and infrared regions due to a "flashing" effect which is inherent in conventional back-side passivated/anti-reflection coated InSb devices.
A conventional passivation/anti-reflection coating is formed by anodization of the back-side, or light receiving surface of the photodetector device substrate. The relative photoresponse of a conventional anodized InSb photodetector as a function of wavelength is illustrated in FIG. 1. It will be seen that the photoresponse rises from a low value in the visible range below 1 micrometer to a peak at approximately 5 micrometers, after which it drops abruptly. This is highly undesirable since the optimal response per photon would be constant at all operating wavelengths.
The prior art approach to utilization of InSb photodetectors for detecting infrared radiation is to provide a filter which selectively prevents light of visible and ultraviolet wavelengths from reaching the device as shown in FIG. 2. This, of course, renders the device inoperative for detecting visible light.
Another problem with InSb photodetectors in the visible wavelength range is an avalanche effect which occurs at less than 0.7 micrometers as is further illustrated in FIG. 1. The photoresponse increases abruptly as the wavelength decreases below this value, rendering the device essentially unusable for detection of radiation of shorter wavelengths due to blooming for imaging applications.